I. Field of the Invention
Chemically modified dialdehyde polysaccharides provide superior hardeners for gelatin compositions. In particular, the use of the specific dialdehyde polysaccharides disclosed herein enables replacement of gelatin with non-gelatin materials at high concentration levels with an improvement in hardening properties.
II. Brief Description of the Prior Art
The use of dialdehyde polysaccharides, particularly dialdehyde starches and gums, as hardeners for gelatin films is known in the art and may be represented by the disclosures in U.S. Pat. Nos. 3,057,723 and 3,058,827 as well as in British Pat. No. 891,221. It is also known and disclosed in U.S. Pat. Nos. 3,865,603 and 3,758,323 that gelatin may be extended with certain chemically modified fluidity or chemically modified thermally converted starches or dextrins. Although it has been found that replacement of the gelatin with the latter starches or dextrins may be made at relatively high levels while maintaining compatibility of the gelatin and starch mixture, the films resulting from such high replacement levels suffer some undesirable reduction in hardness.
For economical reasons, it is apparent that the higher levels of gelatin replacement are desirable and there is thus a need in the art for a superior hardener for gelatin compositions in general and particularly for extended gelatin compositions.